The present invention relates to a molecular beam source for use in accumulation of organic thin-films, for heating a material to be formed on a surface of a solid body or matter, such as, a substrate, etc., in the form of a thin-film, thereby melting and evaporating the film-forming material, i.e., generating evaporated molecules for growing the thin-film upon the surface of the solid body, and it relates to, in particular, a molecular beam source for use in accumulation of the thin-film of an organic material and suitable for accumulating the thin-film of an organic material upon the film forming surface of the solid body, such as the substrate, etc.
In recent years, attention has been paid to organic thin-film elements, such as an organic electroluminescence (i.e., EL) and/or an organic semiconductor as being typical or representative ones thereof. With these thin-film elements, an organic material is heated within a vacuum so as to blast the vapor thereof onto the substrate and then it is cooled down to be solidified or bonded thereon. In general, the following method is applied, wherein an organic material is put into a melting pot or a crucible, which is made of a material having a high melting-point, such as, tungsten, etc., and then the material to be formed into a film is heated up through heating the periphery of the crucible by means of a heater, thereby generating a vapor thereof to be blasted onto the substrate.
However, since most of the organic materials, i.e., the film-forming materials, are inferior, in particular, in the heat conductivity thereof, it is impossible to heat the film-forming material uniformly by the evaporating means as mentioned above and, therefore, there is a drawback that it results into unevenness or non-uniformity in generation of the vapor. It is also apparent that this drawback brings about a further large problem, in particular, of trying to put a large amount of the organic material into the crucible.
As described in the following Patent Document 1, it is proposed to put a material which is thermally and chemically stable, as well as greatly superior to the film forming material in the thermal conductivity thereof, together with the film forming material, into the crucible, thereby obtaining a solution to the drawback mentioned above.
Further, as another drawback relating to the evaporating means of the film-forming material, there is also pointed out an ill effect, i.e., since the vapor of the organic film-forming material can be generated under the condition of a high vapor pressure and low temperature, the vapor of the film-forming material is unintentionally or unexpectedly generated if only putting that material into the crucible and disposing it within a vacuum, and thereby bringing about contamination onto the substrate. For dealing with the drawback mentioned above, there is proposed an idea, as is described in the following Patent Document 2, of adjusting the amount of vapor through a needle valve, while making the crucible into a closed type in the structure thereof.
Patent Document 1: Japanese Patent Laying-Open No. 2003-2778; and
Patent Document 2: Japanese Patent Laying-Open No. 2003-95787.